If it's just a common old kitchen table do what I did.
Take it outside and sand and scrape off all the varnish - rub down well with fine paper and clean off the dust - dress with teak-oil let dry . Give it a couple more coats.
Finish will be much better than original varnish and easier to repair next time it gets scratched, stained or burnt by a careless cigarette.
If you really want it varnished still scrape off original finish - apply three coats of gloss poly-varnish lightly rubbing down after each coat and lastly a coat of matt varnish. Low sheen looks much better and fewer reflections tends to show the grain rather than any small imperfections which are highlighted by a glossy finish.
Peccavi
November 2008